In 2005, NASA’s Cassini spacecraft detected geysers erupting from the surface of Enceladus, an icy moon orbiting Saturn. Since then researchers have continued to study the moon, trying to figure out if it harbors the right stuff to support life under its frosty surface.
The problem is, the Cassini spacecraft, which ended its mission with a fiery dive into Saturn last September, wasn’t properly outfitted to detect life on Enceladus. And there is no mission headed that way anytime soon. So researchers took the question to the lab, modeling conditions on Enceladus, reports Hannah Devlin at The Guardian, and their results suggest that the moon could support certain deep sea microbes found here on Earth.
Modeling the conditions on Enceladus is difficult. That’s because, despite a decade of study, we still don’t know much about it, including just how deep its oceans are. But as Marina Koren at The Atlantic reports, subsequent studies suggest Enceladus' plumes have life-supporting compounds, including methane, ammonia, carbon dioxide, formaldehyde, nitrogen and hydrogen.
So researchers at the University of Vienna created several simulations to model various condition on the moon, varying the pressure to mimic different depths as well as changing pH levels and temperatures. They then introduced three species of methanogenic archaea, a type of microorganism that gobbles up carbon dioxide and hydrogen, producing methane as a waste product. On Earth, some methanogens are extremophiles—known to live deep in the ocean at hydrothermal vents, surviving on the intense heat and chemicals released.
One of those organisms, Methanothermococcus okinawensis, found in hydrothermal vents in the East China Sea could take whatever conditions the researchers dished out, suggesting that a similar creature could possibly survive in Enceladus' oceans. The study appears in the journal Nature Communications.
The researchers were surprised okinawensis' sturdiness. “They’re really robust,” co-author Simon Rittmann tells Devlin. “Life is present under so many different conditions on Earth and researchers who work on the origins of life in different environments keep on extending the boundaries under which it can thrive.”
Hunter Waite, one of the principal investigators on the Cassini mission who was not involved in the study, tells Koren that it’s likely that Enceladus has hydrothermal vents similar to those on Earth. If we could somehow drop okinawensis through the cracks in Enceladus ice, it might be pretty cozy in the extremes of those regions. “This is just a further indication that it’s not a stretch of the imagination at all to think that there might be microbes living in some form in these ocean worlds, even in our own solar system.”
In fact, as Emma Grey Ellis at Wired reports, it’s possible that some of the methane detected in Enceladus’s plumes was created by similar methane-producing creatures. But proving the methane's origins is difficult.
Geochemist Christopher Glein at the Southwest Research Institute says that researchers should now begin to seek ways to distinguish biologically produced methane from chemically produced methane, which would allow a craft passing through one of Enceladus’ geysers to determine whether life exists below. “I’m pleased people are starting to take deep looks at biological methane production,” he says. “The next step is doing this hard work in the lab to figure out what life might look like from a spacecraft instrument’s point of view.”
Waite tells Devlin that such a flyby is doable (Cassini actually did this before its final dive), and is more likely than getting an autonomous submarine into the moon’s ocean—a project that he says probably won’t happen in our lifetimes.
Rittman for his part emphasizes that this study doesn’t prove that there is microbial life on Enceladus, much less intelligent life, he tells Agence-France Presse. It only shows that there could be life, but detecting that is a project for other scientists.